Helping non-relatives: a role for deceit?

In birds and mammals with ‘helpers-at-the-nest’, some individuals not only feed unrelated offspring, but also compete to do so. Non-adaptive explanations for alloparental care do not predict competition for access to offspring that, in its most extreme form, can include kidnapping young from adjacent territories. A common adaptive explanation holds that allofeeding promotes a ‘social bond’, with non-relatives. This proximate hypothesis does not explain why the recipient later cooperates with or helps at the nest of its former benefactor. An extension of this hypothesis posits that, by helping to care for unrelated young, individuals may take advantage of a kin-recognition mechanism based on associations learned by nestlings while being fed. The deceived young later may offer assistance according to its perceived relatedness to the former helper. This mechanism, termed kinship deceit, may be a form of bet-hedging in cooperative breeding systems where mortality is high, where breeders can benefit from contributions by helpers, and where helpers normally assist relatives.